Psoriasis is a T cell-mediated inflammatory disease that is considered to be one of the most common autoimmune diseases, affecting approximately 2% to 3% of adults, though the global prevalence varies widely (Stern R. S., et al., J Investig Dermatol Symp Proc 2004, 9: 136-39; Davidson A and Diamond B. N Engl J Med 2001, 345: 340-50; Langley R. G. B., et al., Ann Rheum Dis 2005, 64(Suppl II): ii18-23). Psoriasis has a major impact on quality of life (de Korte J, et al., J Investig Dermatol Symp Proc 2004, 9: 140-7; Krueger G, et al., Arch Dermatol 2001, 137: 280-4; Finlay A Y and Coles E C, Br J Dermatol 1995, 132: 236-44) and is associated with a number of psychological and psychosocial problems (Kimball A B, et al., Am J Clin Dermatol 2005, 6: 383-92; Russo P A, et al., Australas J Dermatol 2004, 45: 155-9). Many traditional psoriasis therapies have toxic adverse effects; therefore, their long-term use is limited (Lebwohl M. and Ali S., J Am Acad Dermatol 2001, 45: 487-98; Lebwohl M. and Ali S., J Am Acad Dermatol 2001, 45: 649-61). In addition, many patients with psoriasis are dissatisfied with traditional therapies (Stern R S, et al., J Investig Dermatol Symp Proc 2004, 9: 136-39; Finlay A Y and Ortonne J P, J Cutan Med Surg 2004, 8: 310-20); thus, there is a clear need for therapies that are safer and easier to use and that can be prescribed on a long-term basis.
Interleukin-12 (IL-12) and the related cytokine IL-23 are members of the IL-12 superfamily of cytokines that share a common p40 subunit (Anderson E J R, et al., Springer Semin Immunopathol 2006, 27: 425-42). Both cytokines contribute to the development of the type 1T helper cell (Th1) immune response in psoriasis, but each has a unique role (Rosmarin D and Strober B E, J Drugs Dermatol 2005, 4: 318-25; Hong K, et al., J Immunol 1999, 162: 7480-91; Yawalkar N, et al., J Invest Dermatol 1998, 111: 1053-57). IL-12 primarily stimulates differentiation of Th1 cells and subsequent secretion of interferon-gamma, whereas IL-23 preferentially stimulates differentiation of naïve T cells into effector T helper cells (Th17) that secrete IL-17, a proinflammatory mediator Rosmarin D and Strober B E, J Drugs Dermatol 2005, 4: 318-25; Harrington Le, et al., Nature Immunol 2005, 6: 1123-32; Park H, et al. Nature Immunol 2005, 6: 1132-41). The overexpression of TL-12 p40 and TL-23 p40 messenger RNA in psoriatic skin lesions suggests that the inhibition of IL-12 and IL-23 with a neutralizing antibody to the IL-12/23 p40 subunit protein may offer an effective therapeutic approach for the treatment of psoriasis (Yawalkar N, et al., J Invest Dermatol 1998, 111: 1053-57; Lee E, et al., J Exp Med 2004, 199: 125-30; Shaker O G, et al., Clin Biochem 2006, 39: 119-25; Piskin G, et al., J Immunol 2006, 176: 1908-15). Such therapeutic approaches for the treatment of psoriasis are clearly needed in the art.